The mechanisms involved in the process of neurosecretion will be explored in parallel studies of several neurosecretory systems in organ culture. The systems are the hypothalamo-neurohypophysial complex of the guinea pig, the caudal neurosecretory system of teleosts, and the mammalian pineal-subcommissural organ complex. These systems all produce peptide hormones and provide an interface between the two principal communication systems in the animal world: nervous and endocrine. They are transducers which convert nervous input to hormonal output. The proposed work will explore the nature of the controls over the synthesis of these hormones, the process by which they are transported to their storage and release sites, and the mechanism by which they are released into the blood stream. Special emphasis will be placed on defining the inter-relationships among these various stages of the neurosecretory process. Changes in rates of synthesis will be observed by labeling tissues with radioactive amino acids and subsequently isolating the hormones for determination of their specific radioactivity. The transport process will be monitored by observing the amount of labeled hormone transported to the release site. Secretion will be measured by recovering released hormones from the culture medium.